A GRT Description missing

[Pxx-X]

at https://openroad.readthedocs.io/en/latest/main/src/grt/README.html#global-route, what is -overflow_iterations mean? I can't find description of it below.
Thank you!

[rovinski]

The global router is responsible for creating "guides", or rough areas where wires should be routed to connect from source to sink(s). It takes an initial first pass while trying to make sure that there aren't too many wires in one area. Each unit area of the chip has the notion of "capacity" which is the number of wires you could fit through the area if each wire was as dense as possible.

If the global router finishes this first pass and some areas of the chip are over their max capacity, this is called "overflow". The global router can try moving wires around to remove this overflow. There is no guarantee that the router will be successful because it is difficult to see in advance if it is even possible to resolve all overflows.

Thus, the -overflow_iterations argument controls how many of these extra passes to take before the global router gives up and tells the user that the design is not routable (this provides an error which will cause the flow to stop). In ORFS, there is a default limit. But a user can provide their own value if they want the global router to try harder or not as hard.

[eder-matheus]

In addition to @rovinski's answer, this argument was renamed to -congestion_iterations, so that's why you didn't see it in the documentation. I'll update the docs to remove this outdated argument.